Fluted osteotome and surgical method for use

ABSTRACT

A surgical method and tool for expanding an initial osteotomy ( 42 ) to receive a bone implant ( 44 ). An osteotome ( 22 ) having a tapered working end ( 28 ) is inserted into the initial osteotomy ( 42 ). The initial osteotomy ( 42 ) is enlarged by simultaneously rotating and pushing the working end ( 28 ) of the tapered osteotome ( 22 ) into the osteotomy ( 42 ). When rotated in one direction the burnishing edges ( 40 ) concentrate the pushing and rotational force in outward normal and tangential component forces against the interior surface of the osteotomy ( 42 ) to incrementally expand the osteotomy ( 42 ) with little to no removal of bone material ( 46 ). When rotated in the opposite direction the burnishing edges cut the interior surface of the osteotomy. Progressively larger tapered osteotomes ( 22 ) are used until an osteotomy ( 42 ) of predetermined size is achieved.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 13/427,391filed Mar. 22, 2012, which claims priority to Provisional PatentApplication No. 61/466,579 filed Mar. 23, 2011, the entire disclosuresof each are hereby incorporated by reference and relied upon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to osteotomes, and more particularly tosurgical methods for expanding an initial osteotomy to receive animplant.

2. Related Art

An implant is a medical device manufactured to replace a missingbiological structure, support a damaged biological structure, or enhancean existing biological structure. Bone implants are implants of the typeplaced into the bone of a patient. Bone implants may be found throughoutthe human skeletal system, including dental implants in a jaw bone toreplace a lost or damaged tooth, joint implants to replace a damagedjoints such as hips and knees, and reinforcement implants installed torepair fractures and remediate other deficiencies, to name but a few.The placement of an implant often requires a preparation into the boneusing either hand osteotomes of precision drills with highly regulatedspeed to prevent burning or pressure necrosis of the bone. After avariable amount of time to allow the bone to grow on to the surface ofthe implant (or in some cases to a fixture portion of an implant),sufficient healing will enable a patient to start rehabilitation therapyor return to normal use or perhaps the placement of a restoration orother attachment feature.

The present invention is directed toward the preparation of a boneimplant cases where expansion of an initial osteotomy is required. Adental implant is shown in FIG. 1 for exemplary purposes as illustrativeof the preparation steps customary in many bone implant applications.According to current techniques, at edentulous (without teeth) jaw sitesthat need expansion, a pilot hole is bored into the recipient bone toform the initial osteotomy, taking care to avoid the vital structures.The pilot hole is then expanded using progressively wider expanderdevices called osteotomes, manually advanced by the surgeon (typicallybetween three and seven successive expanding steps, depending on implantwidth and length). See for example FIG. 2. Once the receiving hole hasproperly prepared, a fixture screw (usually self-tapping) is screwedinto place at a precise torque so as not to overload the surroundingbone.

The osteotome technique has become widely utilized in situationsrequiring preparation of an osteotomy site by expansion of a pilot hole.By nature, the osteotome technique is a traumatic procedure. Theinstruments are advanced with the impact of a surgical mallet, whichcompacts and expands the bone in the process of preparing osteotomysites that will allow implant placement. (FIG. 2.) Treatment of amandibular site, for example, is often limited due to the increaseddensity and reduced plasticity exhibited by the bone in this region.Other non-dental bone implant sites may have similar challenging densityand plasticity characteristics. Additionally, since the osteotome isinserted by hammering, the explosive nature of the percussive forceprovides limited control over the expansion process, which often leadsto unintentional displacement or fracture of the labial plate of bone indental applications. Many patients do not tolerate the osteotometechnique well, frequently complaining about the impact from thesurgical mallet. In addition, reports have documented the development ofa variety of complications that result from the percussive trauma indental applications, including vertigo and the eyes may show nystagmus(i.e., constant involuntary cyclical movement of the eyeball in anydirection).

More recently, a technique has been developed for dental applicationsthat allow the atraumatic preparation of implant sites by eliminatingthe use of a surgical mallet. This procedure is based on the use of aridge expansion system that includes a bur kit and instruments known asmotor-driven bone expanders, such as those marketed by Meisinger splitcontrol bone management system (Neuss, Germany). First a pilot hole isdrilled at the implant site, then a series of progressively largerexpander screw taps are introduced into the bone by hand or withmotor-driven rotation, which decreases surgical trauma (as compared withhammer taps) while providing superior control over the expansion site.See for example FIG. 3. The thread pattern of the expander screw tapshas been designed to compact bone laterally as the instrument advancesinto the osseous crest. This system allows expansion and preparation ofimplant sites in Type II and III bone, as well as compaction of Type IVbone. The Meisinger split control bone management system may beimplemented with a so-called “expander bur” tool to prepare the initialpilot hole to receive the first expander screw tap. In dentistry, theterm “bur” is usually synonymous with “cutter.” The expander bin toolapparently grinds a taper on the inner wall of the pilot hole osteotomythat will readily accept the tapered shape of the first expander screwtap.

Since they are operated with an electric hand piece, the expander screwtaps can be utilized in the anterior as well as posterior regionswithout impingement of the facial tissues or the positional limitationsimposed by traditional osteotomes (unlike a more traditionalmallet-driven osteotome which cannot easily reach for example the lowermandible posterior). Furthermore, the rotational control of theexpansion permits treatment of the mandibular atrophic ridge. The systemcan be utilized by itself or with osteotomes and surgical drills toassist in the placement of a variety of implant design.

US Publication No. 2006/0121415 to Anitua Aldecoa describes the use ofmotor-driven tools and methods for expanding a human bone for thepurpose of installing a dental implant. Similar to the progressiveillustration shown in FIG. 3, a starter drill is used to create a pilothole followed by the insertion of an expander screw tap type osteotomehaving a conical/cylindrical geometry with progressive cross-section. Asurgical motor is used to rotate the osteotome at relatively low speeds.Another example of this technique is described in U.S. Pat. No.7,241,144 to Nilo et al, issued Jul. 10, 2007. The entire disclosures ofUS Publication No. 2006/0121415 and U.S. Pat. No. 7,241,144 are herebyincorporated by reference.

In the prior art designs involving motor-driven bone expansion, therotary speed of the expander screw tap is locked in a fixed relationshipto the expansion rate of the osteotomy. This is because the expander tapthreads cut into the bone and advance the expander tap deeper into theinitial osteotomy with rotation. The “root” of the expander screw tapdoes the expanding work while vertical advance is controlled by pitch ofthreads and rotation speed. In other words, the thread pitch of theexpander screw tap combined with its taper angle is fixed and cannot bealtered by the surgeon. If a surgeon wishes to expand the bone moreslowly, the only recourse is to turn the expander more slowly.Conversely, if they wish to expand the bone more rapidly. the onlyoption is to turn the expander tool more quickly. Thus, the rate of boneexpansion is a direct and unalterable function of the rate at which thesurgeon turns the expander tool, and the surgeon is unable to vary otherparameters such as pressure and/or rotation rate to achieve an optimumexpansion rate.

The utilization of motor-driven bond expanders served in the past (FIG.3) as an innovative technique offering an atraumatic alternative to thetraditional mallet-driven osteotomes (FIG. 2). These instruments alsoprovide, at least arguably, a favorable increase in the control of thebone expansion, which facilitates implant-site preparation whileallowing universal intraoral use. Nevertheless, there are manyshortcomings of the present motor-driven bone expander screw taptechniques. These shortcomings include a relatively large number ofintermediate progressive expansions steps due to the surgeon's inabilityto disassociate the tool rotation rate from the bone expansion rate. Atypical osteotomy kit for dental applications may include 4-6 expanderscrew taps which make the kit cost relatively expensive. Anotherdisadvantage is that each expander screw tap takes time to install andperhaps an equal amount of time to remove (i.e., un-screw). Because ofthe relatively large number of progressive expansions steps needed, thistranslates to a long surgical procedure which increases patientdiscomfort and procedure cost. Yet another disadvantage is that eachrotary expansion step introduces some degree of error into theosteotomy. In dental applications for example, the surgeon's handcontrolling the advancing expander screw tap is typically locatedoutside the patient's mouth, which is laterally offset from therotational axis of the expander tap. Thus, even though a surgical motormay be used to drive the expander tap, there is a very real possibilitythat the surgeon will introduce the some tilt or wobble inadvertently asthe expander tap is advanced (or withdrawn) thus distorting the intendedshape of the osteotomy or even worse provoking a lateral fracture in thebone.

This inexorable linking of tool rotation rate to bone expansion rate inall prior art rotary expander systems limits surgical control over theimplant process, and in some cases may lead to unnecessary patientdiscomfort. There is therefore a need in the art for an improvedsurgical method for expanding an initial osteotomy to receive an implantin all bone applications, and tools therefor, that provide greatersurgical control, are less costly, less likely to introduce error andthat reduce patient discomfort.

SUMMARY OF THE INVENTION

According to a first aspect of this invention, a surgical method isprovides for expanding an initial osteotomy to receive a bone implant.An osteotome is provided having a tapered working end. The taperedworking end of the osteotome is inserted into an initial osteotomy. Theinitial osteotomy has an interior surface surrounded by bone. Theinitial osteotomy is enlarged by forcibly advancing the osteotome intothe initial osseotomy. The inserting and enlarging steps are repeated,as needed, with progressively larger tapered osteotomes until anosteotomy of predetermined size is achieved. The invention isdistinguished by the working end of the tapered osteotome having one ormore longitudinally extending burnishing edges. The enlarging stepincludes simultaneously rotating and pushing the working end of thetapered osteotome into the osteotomy so that the one or more burnishingedges concentrate the pushing and rotational force through theburnishing edge in outward normal and tangential component forcesagainst the interior surface of the osteotomy to incrementally expandthe osteotomy with little to no removal of bone material.

According to a second aspect of the invention, a surgical method isprovided for expanding an initial osteotomy to receive a bone implant.An osteotome is provided having an upper end and a tapered working end.The working end of the tapered osteotome has one or more longitudinallyextending burnishing edges. The upper end of the osteotome is locked ina drill motor and then rotated in a first rotary direction. The taperedworking end of the osteotome is inserted into an initial osteotomyhaving an interior surface surrounded by bone. The initial osteotomy isthen enlarged by pushing the working end of the tapered osteotome intothe initial osteotomy and simultaneously rotating the osteotome in thefirst rotary direction so that the one or more burnishing edges cutagainst the interior surface of the osteotomy to expand the osteotomy byremoval of bone material. Following this, the locking and the insertingand the enlarging steps are repeated but with a second larger taperedosteotome. The second larger osteotome is rotated in a second rotarydirection by the drill motor which is reverse of the first rotarydirection which has the effect of concentrating the pushing androtational force through the burnishing edge in outward normal andtangential component forces against the interior surface of theosteotomy to incrementally expand the osteotomy with little to noremoval of bone material.

Burnishing is the deformation of a surface due to stressed contact withanother object. Burnishing is commonly used in metalworking as a coldforming process, without actual removal of metal, where a tool is rubbedon the metal surface of the pan with sufficient force to cause plasticflowing of the metal. The technique of burnishing is not commonlyapplied in the bone arts, and is heretofore not been applied in surgicalprocedures to expand an initial osteotomy for the purpose of receiving abone implant.

This invention overcomes the disadvantages and shortcomings of prior artosteotome techniques offering an atraumatic alternative to thetraditional mallet-driven osteotomes without any disadvantages of rotaryexpander screw tap systems. The present surgical method provides ahighly controllable, relatively fast and effective technique forexpanding an initial osteotomy to receive a bone implant. By forciblyrubbing the burnishing edges of the osteotome against the interiorsurfaces of the osteotomy, the bone material is effectively expanded andsimultaneously compressed without creating excessive heat or trauma tothe bone material. By simply rotating the osteotome in the oppositerotary direction, the tool can be made to expand by cutting. Because theconcepts of this invention de-link rotation rate of the tool to the boneexpansion rate, the surgeon is provided with substantially greatercontrol which reduces the possibility for the introduction ofinadvertent lateral forces prevalent with prior art expander screw tapdevices. Surgical procedures according to the present methods can becarried out over less time, thereby resulting in less trauma anddiscomfort for the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 is a modified cross-sectional view through jawbone showing anexemplary dental implant in bone composed of a lower fixture portion andan upper restoration, the dental implant being flanked on either side bynatural teeth;

FIG. 2 is a simplified schematic view illustrating a progressivesurgical procedure according to the prior art wherein an initialosteotomy is progressively expanded to receive a dental implant using atraditional mallet-driven osteotome technique;

FIG. 3 is a view as in FIG. 2 but showing prior art expander screw taptechnique which has seeks to replace the mallet-driven osteotometechnique of FIG. 2;

FIG. 4 is a perspective view of an osteotome according to one embodimentof the present invention;

FIG. 5 is a side elevation view of the osteotome shown in FIG. 4;

FIG. 6 is a cross-sectional view through the working end of theosteotome as taken generally along lines 6-6 in FIG. 5;

FIG. 7 is a cross-sectional view through the working end of an osteotomeas taken generally along lines 6-6 in FIG. 5 but looking the otherdirection which, in use, is downwardly into an osteotomy, with radiallines emanating from the burnishing edges of the osteotome to indicatelaterally outward expansive forces applied through the burnishing edgesto the interior surface of an osteotomy;

FIG. 8 is an enlarged view of the area circumscribed at 8 in FIG. 7 anddepicting the interaction between the burnishing edge of the flute ofthe osteotome and the interior surface of the osteotomy, with radial andlongitudinal forces indicated by arrows;

FIG. 9 is a fragmentary perspective view showing the working end of anosteotome according to one embodiment of this invention having sixstraight flutes;

FIG. 10 is a fragmentary perspective view of an alternative osteotomeconfiguration according to this invention wherein the working end isconfigured with ten spiral flutes;

FIG. 11 is a front elevation view of an osteotome embodiment accordingto this invention including six straight flutes;

FIG. 12 is a front elevation view of a prior art osteotome of themallet-driven type shown for comparison purposes adjacent to theosteotome of FIG. 11;

FIG. 13 is a front elevation view of an alternative embodiment of anosteotome according to the subject invention including six helicallyspiraling flutes shown for comparison purposes adjacent the prior artosteotome of FIG. 12;

FIG. 14A is a simplified cross-sectional view through a bone preparedfor surgical expansion with a pilot drill having created an initialosteotomy site;

FIG. 14B is a view taken generally along lines 14B-14B in FIG. 14A;

FIG. 15A is a simplified surgical procedure showing a progression fromthat of FIG. 14A with a first osteotome having been inserted into theinitial osteotomy to expand the initial osteotomy into a first expandedosteotomy;

FIG. 15B is a view taken generally along lines 15B-15B of FIG. 15A;

FIG. 16A shows a further progression in the surgical procedure from thatof FIG. 15A in which a second osteotome is inserted into the osteotomyand operated in a manner so as to expand the osteotomy further;

FIG. 16B is a view as taken generally along lines 16B-16B in FIG. 16A;

FIG. 17A shows a further progression in the expansion process from thatdepicted in FIGS. 14A and 15A and 16A;

FIG. 17B is a view taken from lines 17B-17B in FIG. 17A;

FIG. 18A shows a further progression in the expansion process from thatdepicted in FIGS. 14A and 15A and 16A;

FIG. 18B is a view taken from lines 18B-18B in FIG. 18A;

FIG. 19A is a cross-sectional view of the region as in FIG. 18A showingthe installation of an implant into the fully enlarged preparedosteotomy;

FIG. 19B is a view as taken along lines 19B-19B in FIG. 19A;

FIG. 20 is a simplified cross-sectional view showing a surgicalprocedure referred to herein as “bounce” where an osteotome according tothe present invention is repeatedly pushed into the osteotomy andwithdrawn while the osteotome remains spinning in a repetitive manner soas to enlarge the osteotomy while enabling the surgeon to manage heatbuild-up and make adjustments on-the-fly;

FIG. 21 is a simplified flow chart depicting the primary steps in thesubject method;

FIG. 22 is a diagrammatic view illustrating by way of example the use ofa surgical kit containing four osteotomes of progressively largerdiameter according to the present invention in combination with areversible drill motor to concurrently prepare three separate osteotomysites in a human jaw using selective reversal of osteotome direction toenlarge each osteotomy either by cutting or burnishing without removingthe osteotome from the surgical drill motor;

FIG. 23 is a cross-sectional view through the working end of anosteotome as in FIG. 7 but showing a reverse rotational direction to cutthe interior surface of the osteotomy (and harvest bone material) ratherthan burnish; and

FIGS. 24A-D depict a cross-section through an osteotomy site showing thecharacteristic cellular structure of bone and the manner in which thebone material surrounding the osteotomy is progressively densified whenone pilot drill and three osteotomes of progressively larger diameteraccording to the present invention are used to enlarge the osteotomy viaburnishing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures wherein like numerals indicate like orcorresponding parts throughout the several views, a burnishing osteotomeaccording to the present invention is generally shown at 22 in FIGS.4-11 and 13. The osteotome 22 comprises a longitudinally extending shank24. The shank 24 has a coupling 26 at one end thereof to attach to arotary input such as from a surgical motor having speed and torquecontrols. The osteotome 22 also includes a working end 28. The workingend 28 extends longitudinally from the shank 24 opposite the coupling26. For dental applications as one example, the working end 28 may havea length of approximately 11-15mm, although longer or shorter lengthsmay also be fashioned to suit the application. As perhaps best shown inFIG. 5, the working end 28 has a taper along at least a portion of itslength. A leading distal tip 30 of the working end 28 defines a minimalouter diameter, and an upper end 32 defines a maximum outer diameter ofthe tapered portion. For dental applications, the difference between theminimal outer diameter (at 30) and the maximum outer diameter (at 32) ispreferably 1mm, although larger or smaller differences can be achievedwith larger or smaller taper angles. Of course, for non-dentalapplications involving larger bone osteotomy sites, the dimensionalscale of the osteotome 22 will typically be much larger.

Referring now to the cross-sectional views of FIGS. 6-8, the working end28 is shown including a root shaft 34, from which at least one, but morepreferably a plurality of flutes 36 extend. The plurality of flutes 36may comprise at least three flutes 36. Preferably, the plurality offlutes 36 are equally circumferentially spaced from one another so thatif for example there are four flutes 36 they are arranged 90° apart; sixflutes 36 would be arranged 60° apart; eight flutes 36 would be arranged45° apart; ten flutes 36 would be arranged 36° apart; and so on. Thenumber of flutes 36 may be dictated for primarily practical reasons bythe size of the osteotome 22, such that very small diameter osteotomes22 have the fewest number of flutes 36 and progressively largerosteotomes 22 have progressively more flutes 36.

Each flute 36 extends radially outwardly to a crest 38 which defines themajor diameter of the working end 28 as a function of length. That isbecause the working end 28 is tapered, its diameter changes along itslength. Therefore the major diameter adjacent the distal tip 30 will besmaller than the major diameter adjacent the upper end 32. Thus, themajor diameter is a function of length measured as it were from thedistal tip 30. As perhaps best shown in FIG. 8, a longitudinallyextending burnishing edge 40 is disposed along the outermost portion ofthe crest 38. The burnishing edge 40 is that specific portion of thecrest 38 which lies along the major diameter of the tapered working end28. In the embodiments illustrated in the drawing figures, theburnishing edge 40 in each instance is non-rotatably fixed relative tothe root shaft 34. In applications such as dentistry where therelatively small osteotome sizes introduce practical manufacturingconstraints, the burnishing edge 40 may take the form of a fixed ridgethat is unitary (monolithic) with the flutes 36 and entire working end28 of the osteotome 22. However, if manufacturing techniques and otherpractical constraints permitted, the burnishing edge 40 could be formedby a roller element in order to reduce friction and better manage heatbuild-up.

Returning again to FIG. 8, the crest 38 is shown as establishing a largenegative rake angle leading up to the burnishing edge 40. A rake is anangle of slope measured from the leading face of the tool (the crest 38in this case) to an imaginary line extending perpendicular to thesurface of the worked object (e.g., inner bone surface of theosteotomy). Rake angle is a parameter used in various cutting andmachining processes, describing the angle of the cutting face relativeto the work. There are three types of rake angles used in metal working:positive, negative, and zero. However, in the preferred embodiment ofthis present application of a burnishing technique, a negative rakeangle is employed, and more preferably a large negative rake angle.While the actual angle of the negative rake is adaptable to suit theparticular specifications, including the relative roundness or sharpnessof the burnishing edge 40, negative rake angles greater than about 45° ,and even more preferably greater than 60° , have been found to producesatisfactory results. The large negative rake angle of the presentosteotome 22 applies outward pressure at the burnishing edge 40 tocreate a compression wave ahead of the point of contact, loosely akin tospreading butter on toast. Downward pressure applied by the surgeon isneeded to keep the burnishing edge 40 in contact with the bone surfaceof the osteotomy being expanded, that is, to keep it pushing on thecompression wave. This is aided by the taper effect of the osteotomy andtool 22 to create lateral pressure (i.e., in the intended direction ofexpansion). The harder the surgeon pushes down, the more pressure isexerted laterally. This gives the surgeon complete control of theexpansion rate irrespective to a large degree on the rotation speed ofthe osteotome 22. Thus, the burnishing effect's intensity depends on theamount of force exerted on the osteotome 22. The more force exerted, thequicker expansion will occur. The burnishing edges 40 along therespective crests 38 of the flutes 36 lap against bone and do theexpanding work as the osteotome 22 is rotated in combination withdownward pressure applied by the surgeon.

As shown in the enlarged and somewhat exaggerated for clarity FIG. 8, asthe burnishing edge 40 drags across the bone, the force on theburnishing edge 40 can be decomposed into two component forces: onenormal to the bone's surface, pressing it outwardly, and the othertangential, dragging it along the inner surface of the osteotomy. As thetangential component is increased, the burnishing edge 40 will start toslide along the bone. At the same time, the normal force will deform thesofter bone material. If the normal force is low, the burnishing edge 40will rub against the bone but not permanently alter its surface. Therubbing action will create friction and heat, but this can be controlledby the surgeon by altering, on-the-fly, the rotation speed and/orpressure and/or irrigation flow. As will be described subsequently inconnection with FIG. 20, because the working end 28 of the osteotome 22is tapered, the surgeon may at any instant during the surgical procedurelift the burnishing edges 40 away from contact with the surface of thebone to allow air cooling and/or irrigation. This can be done in acontrolled “bouncing,” i.e., axially reciprocating, fashion wherepressure is applied in short bursts with the surgeon continuouslymonitoring progress and making fine corrections and adjustments.Conversely, as the normal force increases, eventually the stresses inthe bone's surface exceed its yield strength. When this happens, theburnishing edge 40 will plow through the surface and create a troughbehind it. The plowing action of the burnishing edge 40 thusprogressively enlarges the osteotomy. While the elastic properties ofbone are well-known, if the load imposed exceeds the bone's ability todeform elastically, it will deform further and change shape permanentlyby plastic deformation. The permanent change in shape is believed to beassociated with micro-cracks that allow energy release, a compromisethat is a natural defense against complete fracture. If thesemicro-cracks are small, the bone remains in one piece while theosteotomy expands. Forcibly pushing the rotating working end into theosteotomy causes the burnishing edges to sweep against the interiorsurface of the osteotomy and thereby expand the osteotomy by incrementalplastic deformations that cause a progressive enlargement of theosteotomy beginning adjacent the open end and developing in afrustoconical pattern downwardly into the osteotomy.

Expansion of the osteotomy occurs when the burnishing edge 40 is rotatedagainst the bone surface of the osteotomy and downward pressure isapplied by the surgeon. This has the effect of causing, at the same timerotation and translation of the burnishing edge 40, but in a manner thatdoes not positively link rotation and translation as in prior artexpander screw tap devices. The osteotomy, therefore, is formed into thefinal size ready to receive the fixture portion of an implant by aseries of small incremental plastic deformations created by sweeps ofsuccessive burnishing edges 40 pressed hard against the interior surfaceof the osteotomy. Each such plastic deformation is followed by a shortinterval of rest before the arrival of the next successive burnishingedge 40. Additional discussion concerning the effects of burnishing onthe bone structure is described below in connection with FIGS. 24A-D.

The burnishing edge 40 is shown in FIG. 8 comprising a chisel-like shapeheld at the previously described large negative rake angle. However,those of skill will appreciate that the burnishing edge 40 could beformed by other crest 38 profile shapes, such as rounded or lobeddesigns, provided the manufacturing techniques required to make such analternative profile were found to be cost-justified in comparison withthat of the profile as shown in FIGS. 7 and 8. Furthermore, as describedbelow in connection with FIG. 23, the chisel-like shape of the preferredembodiment is useful as a cutting tool when rotated in reversedirection.

Turning now to FIGS. 9-13, the illustrations depict various embodimentin which the flutes 36, and thus by extension the burnishing edges 40,may be formed either with no twist, i.e., straight as in FIGS. 9 and 11,or with a spiral twist along, the length of the working end 28 as inFIGS. 10 and 13. A prior art osteotome of the mallet-driven type isshown for side-by-side comparison purposes in FIG. 12. The spiralingdirection of the flutes 36 can be set to either raise debris out of theosteotomy when rotated in a clockwise direction or push debris down intothe osteotomy when rotated in a clockwise direction. Said another way,spiraling direction of the flutes 36 can be set to either raise debrisout of the osteotomy when rotated in a burnishing direction or pushdebris down into the osteotomy when rotated in a burnishing direction.The osteotomes 22 shown in FIGS. 22 and 24A-D, for example, are arrangedwith flute 36 spirals that tend to lift debris out of the osteotomy whenrotated in a counter-clockwise (burnishing) direction.

By way of example, FIGS. 14A-20 depict a progression of surgical stepsfor expanding an initial osteotomy 42 to receive a dental implant 44.Although a dental example is used in FIGS. 14A-20 and 22 must beappreciated that the present invention can be used in non-dentalsurgical procedures, such as those applied by orthopedic surgeons andperhaps any other procedure requiring creation or enlargement of anosteotomy site with the beneficial bone densification attributes of thepresent invention. Typically as a first step an initial osteotomy siteis prepared by exposing bone 46, and then drilling a pilot hole into thebone 46 with a pilot drill 48. This is shown in FIG. 14A, and may beaccomplished with a typical prior art surgical pilot drill 48 turned ina standard clockwise direction. The pilot hole in this instancecomprises the initial osteotomy 42. In some cases, the surgeon maydecide it is beneficial to saw a groove 50 along the bone ridge as seenin FIG. 14B. The sawed groove 50 typically intersects the pilot hole 42along the ridge of the bone 46. The surgeon may decide to first drillthe pilot hole and then saw the groove 50, or vice versa, it beingunderstood that the groove 50 is an ancillary surgical feature.

A first osteotome 22 according to the present invention is operativelyconnected to a surgical motor (not shown) though its coupling 26feature. Then the working end 28 of the first osteotome 22 is insertedinto an initial osteotomy 42. The interior surface of the initialosteotomy 42 is surrounded by bone 46. If the diameter of the pilotdrill 48 is, for example 15 mm, then preferably the major diameter ofthe working end 28 of the first osteotome 22 adjacent the leading distaltip 30 is also 1.5 mm so that it follows easily the pilot hole. Becauseof the widening taper, the major diameter of the working end 28 adjacentthe upper end 32 is larger than the initial osteotomy. This may be, forexample, 2.5 mm. At these exemplary dimensions, a first osteotome 22having four equally spaced flutes 36/burnishing edges 40 of straight orhelical twist has been found to provide satisfactory results. More orfewer flutes 36/burnishing edges 40 are certainly possible.

The initial osteotomy 42 is enlarged in a next step of the procedure byforcibly advancing the working end 28 of the first osteotome 22 into theinitial osseotomy 42 to the desired depth, which is depicted in FIG.15A. Depth markings in the form of laser-etched stripes may be appliedto the working end 28 to indicate customary depths (as measured from thedistal tip 30) of, for example, 7mm, 10mm, 13mm and 15mm. This forcibleadvancing includes simultaneously rotating and pushing the working end28 of the first tapered osteotome 22 into the osteotomy 42 so that itsone or more burnishing edges 40 concentrate the pushing and rotationalforce in outward normal and tangential component forces (FIG. 8) againstthe interior surface of the osteotomy 42. FIG. 15A illustrates acounter-clockwise rotation of the osteotome 22, but that direction ismerely preferred and can be reversed with suitable alterations made tothe shape and/or rake angle of the osteotome 22. Although the surgeonmay vary the rotational speed of the osteotome 22 according to thedictates of the situation in their judgment, experimental resultsindicate that rotation speeds between about 200-1200 RPM and torquesettings between about 15-50 Ncm provide satisfactory results. Morepreferably rotation speeds between about 600-1000 RPM and torquesettings between about 20-45 Ncm provide satisfactory results. And stillmore preferably, rotation speeds in the range of 800-900 RPM and torquesettings of about 35 Ncm provide satisfactory results.

As perhaps best shown in FIG. 20, the enlarging step may include thecontrolled practice of bouncing the burnishing edges 40 into and out ofcontact with the interior surface of the osteotomy 42 while continuouslyrotating the osteotome 22. This practice is unachievable using prior artosteotome tools and techniques (as shown in FIGS. 2, 3 and 12). However,because the subject osteotome 22 has a tapered working end 22 and onlythe burnishing edges 40 are in contact with the interior surface of theosteotomy 42, the surgeon may at any time lift the working end 28 out ofcontact to evaluate progress, manage heat, irrigate, adjust approach, ormake other corrections. In fact, the surgeon may practice a verycontrolled technique whereby the burnishing edges 40 are repeated andsuccessively pushed into and pulled out of the osteotomy 42 in a sort ofbouncing maneuver. Although this bouncing technique is not required forproper execution of the method, the novel tool shape and other featuresof this invention enable the bouncing technique if and whenever thesurgeon warrants.

It should also be mentioned that if the surgeon warrants, the osteotome22 may be rotated in the opposite direction (e.g., clockwise in theseexamples) and utilize the osteotome 22 to enlarge the osteotomy 42 bycutting or excavating bone material from the osteotomy 42 rather thanvia compression and plastic deformation. This technique of reversingrotation of the osteotome 22 as an intentional step during the surgicalexpansion procedure is described more fully below in connection withFIGS. 22 and 23.

When the desired depth (approximately 6-20 mm in dental applications;significantly larger in other medical applications) of the working end28 has been advanced into the osteotomy the resultant effect is anincremental expansion of the osteotomy 42 to the dimensions of theworking end 28 with little to no removal of bone material 46. The firstosteotome 22 is then removed from the osteotomy 42 to reveal a firstenlarged osteotomy 42. The first enlarged osteotomy 42 is fully preparedand ready to receive an implant 44 if, in this example with the givendimensions, its fixture portion is sized at about a 3.0mm diameter.

If the fixture portion of the implant 44 is larger than 3.0mm(continuing with this dental-specific example for purposes ofillustration), then the first enlarged osteotomy 42 must be enlargedstill further. This is accomplished by repeating the inserting andenlarging steps with progressively larger tapered osteotomes 22, asneeded, until an osteotomy 42 of predetermined size is achieved. Morespecifically, as shown in FIG. 16A, a second osteotome 22 having atapered working end 28 that is larger in diameter than the firstosteotome 22, is operatively connected to the surgical motor (notshown). The tapered working end 28 of the second osteotome 22 isinserted into the first enlarged osteotomy 42. Using the previouslydescribed exemplary dimensions, the major diameter of the working end 28of the second osteotome 22 adjacent the leading distal tip 30 is 2.5mmso that it follows easily the first enlarged osteotomy 42. Because ofthe widening taper, the major diameter of the working end 28 adjacentupper end 32 is, for example, 3.5 mm. At these exemplary dimensions, thesecond osteotome 22 having six equally spaced flutes 36/burnishing edges40 of straight or helical twist has been found to provide satisfactoryresults. More or fewer flutes 36/burnishing edges 40 are certainlypossible.

The surgeon proceeds to further enlarge the first enlarged osteotomy 42by forcibly advancing the second osteotome 22 into the first enlargedosteotomy 42 to create a second enlarged osteotomy 42. As before, theadvancing step is comprised of simultaneously rotating and pushing theworking end 28 of the second tapered osteotome 22 to a desired depthinto the osteotomy 42 so that its one or more burnishing edges 40concentrate the pushing and rotational force in outward normal andtangential component forces (FIG. 8) against the interior surface of theosteotomy 42. When the full length (approximately 11-15mm) of theworking end 28 has been advanced into the osteotomy 42, the secondosteotome 22 is then removed from the osteotomy 42 to reveal a secondenlarged osteotomy 42. The second enlarged osteotomy 42 is fullyprepared and ready to receive an implant 44 if in this example with thegiven dimensions, its fixture portion is sized at about a 4.0mmdiameter.

If the fixture portion of the implant 44 is larger than 4.0mm(continuing with this dental-specific example for purposes ofillustration), then the second enlarged osteotomy 42 must be enlargedstill further. This is accomplished by repeating the inserting andenlarging steps with a progressively larger tapered osteotome 22. FIG.17A illustrates this scenario where a third osteotome 22 is operativelyconnected to the surgical motor. Its tapered working end 28 is insertedinto the second enlarged osteotomy 42. Using the previously describedexemplary dimensions, the major diameter of the third osteotome 22adjacent its leading distal tip 30 is 3.5mm, and adjacent its upper end32 may, for example, be 4.5mm. At these exemplary dimensions, the thirdosteotome 22 may have eight equally spaced flutes 36/burnishing edges 40of straight or helical twist, although more or fewer flutes36/burnishing edges 40 are certainly possible.

The surgeon proceeds to further enlarge the osteotomy 42 bysimultaneously rotating and pushing the working end 28 of the thirdtapered osteotome 22 into the osteotomy 42 so that its one or moreburnishing edges 40 concentrate the pushing and rotational force inoutward normal and tangential component forces (FIG. 8) against theinterior surface of the osteotomy 42. When the desired depth(approximately 7-15mm) of the working end 28 has been advanced into theosteotomy 42, the third osteotome 22 is then removed from the osteotomy42 to reveal a third enlarged osteotomy 42. The third enlarged osteotomy42 is fully prepared and ready to receive an implant 44 if, in thisexample with the given dimensions, its fixture portion is sized at abouta 5.0mm diameter.

If the fixture portion of the implant 44 is larger than 5.0mm(continuing with this dental-specific example for purposes ofillustration), then the third enlarged osteotomy 42 must be enlargedstill further. This is accomplished by repeating the inserting andenlarging steps with a progressively larger tapered osteotome 22. FIG.18A illustrates use of a fourth osteotome 22 having (for example) amajor diameter adjacent its leading distal tip 30 of 4.5mm, and adjacentits upper end 32 of 5.5mm. At these exemplary dimensions, the fourthosteotome 22 may have ten equally spaced flutes 36/burnishing edges 40of straight or helical twist, although more or fewer flutes36/burnishing edges 40 are certainly possible.

The surgeon proceeds to further enlarge the third enlarged osteotomy 42by simultaneously rotating and pushing the working end 28 of the fourthtapered osteotome 22 into the osteotomy 42. As before, the one or moreburnishing edges 30 concentrate the pushing and rotational forcesagainst the interior surface of the osteotomy 42. When the desired depth(approximately 7-15mm) of the working end 28 has been advanced into theosteotomy 42, the fourth osteotome 22 is then removed from the osteotomy42 to reveal a fourth enlarged osteotomy 42. The fourth enlargedosteotomy 42 is fully prepared and ready to receive the implant 44 if,in this example with the given dimensions, the fixture portion is sizedat about a 6.0mm diameter.

To complete the example, FIG. 19A shows the 6.0mm diameter fixtureportion of an implant 44 installed into the fourth enlarged osteotomy42. The step of installing a fixture portion of an implant 44 includesdirectly engaging an exterior anchoring thread form 52 of the fixtureportion into the expanded osteotomy formed by the burnishing edge 40.

FIG. 21 provides an exemplary flow diagram of the method of thisinvention according to one preferred method. The surgical method of thisinvention, and in particular the diameter to which the osteotomy 42 canbe ultimately expanded, is of course limited by the physical propertiesof the bone 46 and other factors. In other words, the steps of expandingas described herein are directly related to the final desired fixture 44diameter but also related to the ability of the bone 46 to plasticallydeform (via the above-described micro-cracks) without fracturing. Forexample, in some conditions it is not possible for even a skilledsurgeon to take a 3mm width of bone 46 and use the procedures of thisinvention to expand an osteotomy 42 all the way to 5.5mm withoutfracturing the bone 46. However, it may be possible to expand theosteotomy 42 to a slightly smaller 4.5mm so that it will receive a 5mmdiameter implant 44. Thus, it should be understood that bone's abilityto plastically deform without fracturing dictates how much expansion canbe achieve, and also dictates at which step the surgeon must to stop theexpansion process to avoid fracturing the bone 46 and/or the use ofcounter-rotation cutting as described below in connection with FIG. 22.

The surgical method of this invention enables an expansion of an initialosteotomy 42 to receive a bone implant 44 that is significantly lesstraumatic than other prior art osteotome techniques, that is faster thanother prior art osteotome techniques, that is able to reach previouslydifficult to reach areas (e.g., the lower mandible posterior), thatrequires fewer progressive steps (and tools) to achieve a final enlargedosteotomy than other prior art osteotome techniques, and that issignificantly better at managing heat build-up than other prior artosteotome techniques. Heat management is enhanced through irrigationinto the osteotomy (difficult with prior art techniques) and also bymaintaining a separation space between the root shaft 34 and the boneinterior surface of the osteotomy 42. This separation space means lessfriction and also the opportunity for some degree of convective cooling.

FIG. 22 is a diagrammatic view illustrating by way of example the use ofa surgical kit containing four osteotomes 22A-D of progressively largerdiameter according to the present invention in combination with areversible surgical drill motor 60 to concurrently prepare threeseparate osteotomy sites 62, 64 and 66, respectively, in a human jawbone 46 using selective reversal of osteotome direction to enlarge eachosteotomy either by cutting or burnishing without removing a givenosteotome 22 from the surgical drill motor 60. Although the example ispresented here again in the context of a dental application, those ofskill in the art will appreciate that the described techniques areadaptable to non-dental applications including, but not limited to,joint replacement and bone fixations generally.

In this example, a first osteotomy site 62 is located in the front ofthe mandible bone 46 where the bone width is relatively narrow. Thecomposition of the bone 46 in the region of the first osteotomy site 62may be described as predominantly Type II. A second osteotomy site 64 islocated slightly posterior of the first site 62 in a region of themandible that has moderate bone 46 width. The composition of the bone 46in the region of the second osteotomy site 64 may be described asgenerally a combination of Types II and III. A third osteotomy site 66is located in a molar region of the mandible and is surrounded by arelatively generous bone 46 width. The composition of the bone 46 in theregion of the third osteotomy site 66 may he described as predominantlyType III. Due to the varying width and composition of bone 46 at sites62, 64 and 66, the surgeon does not wish to apply exactly the sametechnique and procedure to each osteotomy. The novel attributes of thepresent invention give the surgeon the ability to concurrently prepareall three osteotomy sites 62-66 in different ways.

In this example each osteotomy site 62-66 is presumed to have an initialosteotomy prepared by first drilling a pilot hole of 1.5mm. (Of course,the circumstances of any given surgical application, whether dental ornon-dental in nature, will dictate the size of initial osteotomy andother characteristics of the operation.) The surgeon locks or otherwiseinstalls the first osteotome 22A into the drill motor 60 and sets therotational direction to counter-clockwise. The surgeon then pushes thefirst osteotome 22A into the first osteotomy site 62 in the mannerdescribed above to expand through burnishing. However, due to thedifferent compositional nature of the second 64 and third 66 osteotomysites, the surgeon chooses to enlarge by cutting rather than burnishing.To affect this, the surgeon reverses the rotational direction of thedrill motor 60 to clockwise without removing the first osteotome 22Afrom the drill motor 60. Then, using a similar pushing motion, thesurgeon enlarges the second 64 and third 66 osteotomy sites by removingbone material which may, if desired, be harvested. FIG. 23 represents across-sectional view through the working end of an exemplary osteotome22 as in FIG. 7, but showing a reverse rotational direction to cut theinterior surface of the osteotomy 62 and harvest bone material (shown aschips or shavings in front of burnishing edge 40).

At this stage in the hypothetical example, the first osteotomy site 62has been expanded as much as the surgeon desires; no further expansionis needed of the first osteotomy site 62. However, the second 64 andthird 66 osteotomy sites both require additional expansion. The surgeonthen installs the second osteotome 22B into the drill motor 60 and setsthe rotational direction to counter-clockwise. Skipping the completedfirst osteotomy site 62, the surgeon then expands the second osteotome22B into the second osteotomy site 64 through burnishing in the mannerdescribed above. Due to the different compositional nature of the thirdosteotomy site 66, the surgeon chooses to enlarge by cutting rather thanburnishing. To affect this, the surgeon reverses the rotationaldirection of the surgical motor 60 to clockwise without removing thesecond osteotome 22B from the surgical motor 60. Then, using a similarpushing motion, the surgeon enlarges the third osteotomy site 66 byremoving bone material (which may, if desired, be harvested).

Once the remaining two osteotomy sites 64, 66 have been enlarged by thesecond osteotome 22B, the surgeon locks or otherwise installs the thirdosteotome 22C into the drill motor 60 and sets the rotational directionto counter-clockwise. Again skipping the completed first osteotomy site62, the second 64 and third 66 osteotomy sites are enlarged byburnishing. In both cases, the surgical motor 60 is set to turn in thecounter-clockwise direction. The second osteotomy site 64 has now beenexpanded as much as the surgeon desires; no further expansion is neededof the second osteotomy site 66. However, the third osteotomy site 66still requires additional expansion. Therefore, the surgeon installs thefourth osteotome 22D into the drill motor 60 and sets the rotationaldirection to counter-clockwise. Skipping the completed first 62 andsecond 64 osteotomy sites, the third 66 osteotomy site is enlarged byburnishing using the previously described techniques. Implants (orfixture portions of implants) can now be installed at each osteotomysite 62-66. The surgeon places a 3.0-3.25 mm implant into the firstosteotomy site 62, a 5.0 mm implant into the second osteotomy site 64,and a 6.0 mm implant in the third osteotomy site 66.

Those of skill in the art will recognize the substantial improvement inconvenience and efficiency the present invention affords by allowing asurgeon to concurrently prepare a plurality of osteotomy sites coupledwith the ability to expand one site by burnishing and another site bycutting without removing the osteotome 22 from the drill motor 60. Thisadvantage is of course not exclusive to concurrent multi-siteapplications, and is in addition to the previously described advantagesof significantly reduced trauma, increased speed, improved access todifficult areas, and better heat management.

FIGS. 24A-D depict a cross-section through a typical osteotomy siteshowing the characteristic cellular structure of bone 46 and the mannerin which the bone material surrounding the osteotomy 42 is progressivelydensified when one pilot drill 48 and three osteotomes 22A-C ofprogressively larger diameter according to the present invention areused to enlarge the osteotomy 42 via the present burnishing technique.

Bränemark classification of bone includes type I, II, III and IV. Type Iis homogeneous compact bone: Type II bone has a thick cortical layer anda dense core; Type III bone has a thin cortical layer and a trabecularcore of good strength: Type IV bone has a thin cortical layer and acancellous core of poor strength. A dense crestal cortex is generallyfavored for initial fixation of an implant. Often the implant can beplaced to take advantage of one or both of the buccal and lingualcortical plates. Placing implants in Type III and IV bone is morechallenging that in Types I and II. Moreover, the quality of bone can beextremely variable in a single location. It is likely that at someosteotomy sites the bone 46 may contain voids, fatty marrow, and fibrousinclusion. When the surgeon encounters softer bone texture, the abilityto drill accurately diminishes with the loss of tactile sensitivity.Also, inadvertent over-penetration and over-preparation of soft bone iscommon. Other factors, such as torqueing of the hand piece andreproducing a consistent angle of penetration, become more demanding asbone density decreases.

Use of the present invention to expand an osteotomy by burnishing helpsto maintain all of the existing bone 46 material by pushing the boneaside with minimal trauma while developing an accurately shapedosteotomy 42. Compare the progressive expansion shown in FIGS. 24A-24Dto note the condensing and compacting cellular structure of the bone 46as progressively larger osteotomes 22A-C are introduced. In addition,the osseous layer around the osteotomy 42 is compacted, which will forma denser bone interface with the implant 44 and thus improved retention.This benefit is particularly relevant when there is a marginal quantityof bone 46 to start with.

Drilling and cutting, by contrast, take bone away from a site. Duringthe drilling process, there is no practical means to immediately improveadjacent bone quality. With the present rotary osteotome technique, thebone layer next to the osteotomy 42 is improved because of thecompaction of bone which in turn helps anchor a newly placed implant 44.Drilling does not improve local anatomy or bone quality. The presentosteotome 22 is effective to expand the surrounding bone (e.g. in ridgeapplications) and improve bone quality. The present osteotome 22techniques offer a useful and predictable procedure, improved tactilesensitivity, improved control, and improved implant placement in softbone conditions.

The foregoing invention has been described in accordance with therelevant legal standards, thus the description is exemplary rather thanlimiting in nature. Variations and modifications to the disclosedembodiment may become apparent to those skilled in the art and fallwithin the scope of the invention.

What is claimed is:
 1. A low-impact surgical method for expanding anosteotomy using high-speed rotation, said method comprising the stepsof: providing a rotary osteotome having a tapered working end, theworking end having a plurality of longitudinally extending burnishingedges; positioning the tapered working end of the osteotome over an openend of an osteotomy, the osteotomy having an interior surface surroundedby bone; rotating the working end of the osteotome at high speed; andenlarging the osteotomy by axially bouncing the rotating working endwithin the osteotomy so that the burnishing edges lap against the boneinterior surface with downward motion and separate from the interiorsurface with upward motion in ever deepening movements that cause aprogressive plastic deformation of the bone interior surface beginningadjacent the open end and developing downwardly into the osteotomy. 2.The surgical method of claim 1, wherein the working end of the osteotomeincludes a root shaft, and wherein said enlarging step includesmaintaining a separation space at all times between the root shaft andthe interior surface surrounded by bone.
 3. The surgical method of claim2, wherein a plurality of flutes extend from the root shaft, each saidflute extends radially outwardly to a crest defining the major diameterof the osteotome, each burnishing edge disposed along the crest of arespective one of the flutes, and said enlarging step further includingmanually applying variable axial pressure during said downward motion.4. The surgical method of claim 2, wherein the plurality of burnishingedges are non-rotatably fixed relative to the root shaft.
 5. Thesurgical method of claim 2, wherein the plurality of burnishing edgesare defined by a large negative rake angle.
 6. The surgical method ofclaim 1, wherein said rotating step includes rotating the working end ofthe osteotome at speeds between about 200-1200 RPM.
 7. The surgicalmethod of claim 1, wherein said rotating step includes applying a torqueto the working end of the osteotome between about 15-50 Ncm.
 8. Thesurgical method of claim 1, further providing a second larger taperedosteotome having a greater number of burnishing edges than the firstosteotome.
 9. The surgical method of claim 1, further includinginstalling a fixture portion of an implant into the enlarged osteotomy,wherein said step of installing a fixture portion includes directlyengaging an exterior anchoring thread form of the fixture portion intothe enlarged osteotomy formed by the plurality of burnishing edges. 10.The surgical method of claim 1, wherein the plurality of burnishingedges each have a spiral twist along the length of the working end. 11.The surgical method of claim 1, wherein the plurality of burnishingedges each have a generally straight configuration along the length ofthe working end.
 12. The surgical method of claim 1, further includingthe step of preparing an initial osteotomy site by drilling a pilot holeinto the bone.
 13. The method of claim 1, further including irrigatingthe osteotomy concurrently with said enlarging step.